Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

Model 680 interstage transformer.
#1

Hello  Does anyone know what the D.C. resistance readings should be on the input transformer between the 42 and the 6A3s? I am not getting signal past the plate of the 42 driver tube. plate voltage on the 6A3 s is 290 grid voltage is -63 volts on both tubes. Thanks in advance. Norman
#2

Hi Va.
Looks like pri is 475 ohms sec is 1k ohms g to g. Interesting I checked to see if the bias was too high at -63v but that about right  Just for grins you can put a cap for the plate side to one of the grids. Tipically the secondary will go open and you'll loose bias one one or both output tubes.

When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!

Terry
#3

Terry: Thanks for the fast reply my pri reads 451 Ohms  secondry one side reqads 431 Ohms the other side reads 520 ohms  taken with digital ohmmeter. Are there any replacements availible? thanks again  Norman
#4

Resistance seems ok. What are you using to detect the audio signal? Just for laughs pull the 6A3's out and see if you have a signal on pin 3 on either tube.

When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!

Terry
#5

Radioroslyn: I am using the aux input of a stereo receiver. Getting clean signal from the plate of the 42 driver tube through a .01 mfd cap. tried the grid lead of the 6A3.  no signal at all not even a weak one. Thanks for your help. Norman
#6

That's odd that you've got the proper resistance for the winding and it's not shorted to gnd as you wouldn't have the bias voltage on the 6A3 grids but it's not passing any audio. Mechanically it's like the core is missing!

https://www.tubesandmore.com/products/tr...i-158k-sec
Looks like the ticket.

GL

When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!

Terry
#7

Got it going  was'nt the interstage transformer. now just weak audio but it is crystal clear  no hum or distortion so will have to find out what stage is weak  Thanks for your help  Norman




Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
Jackson 715 not working
Now that you posted the schematic, I don't know why that Sprague electrolytic cap is across the meter, as it is not indi...MrFixr55 — 05:51 PM
HiFi (Chifi) tube amp build - but my own design.
What may be lacking in the PP Tube amps may be the 2nd harmonics, which some, especially RCA back in the day called &quo...MrFixr55 — 05:32 PM
Jackson 715 not working
Usually in an emission tester, the tube under test is measured as if it were a diode. So, some testers connect all the g...RodB — 04:17 PM
Restoring Philco 37-604C
Yep. F5 is green, D5 is Red. Red is Bad. Green is Clean.morzh — 01:30 PM
Jackson 715 not working
I did start to do that but I stalled out because I could not figure out how the grid and plate get voltage. In this diag...daveone23 — 11:52 AM
Restoring Philco 37-604C
(Insert Homer Simpson "DOPF" Here.) When all fails, look at the can. Took the Ron Ramirez advice, red Caig D...MrFixr55 — 09:23 AM
Philco 91 Speaker Replacement
From your text I am not sure if you intend to use the existing speaker with a resistor instead of the field coil. It wo...morzh — 08:44 AM
Philco 91 Speaker Replacement
My field coil is bad. I am still hoping to find an original, but if I can't I will go with a fitting Philco speaker, 125...dconant — 08:34 AM
Philco 91 Speaker Replacement
As Rod said, it is OK to use a fitting speaker, and then look for an original one. If you buy a Hammond 125 output tr...morzh — 08:15 AM
Philco 91 Speaker Replacement
Yes, I often have to substitute, then keep an eye out for an original. In the meantime, the radio is working and being e...RodB — 08:02 AM

[-]
Who's Online
There are currently no members online.

>